Traction devices are known that pull mouthpieces to be attached to maxillae inside mouths of human bodies. FIG. 1 illustrates a traction device 900 described in Japanese Laid-open Patent Publication No. 2009-89928 including an engaging assembly 902 that engages with a mouthpiece 901 and a support assembly 903 that supports the engaging assembly 902 in contact with a face of the human body. The engaging assembly 902 pulls the mouthpiece 901 in the anterior direction of the human body.
The support assembly 903 includes an upper contact body 904 that comes into contact with the forehead of the face and a lower contact body 905 that comes into contact with the lower edge of the mandible of the face. The upper contact body 904 and the lower contact body 905 receive a reaction force F2 generated in reaction to a force F1 from the engaging assembly 902 pulling the mouthpiece 901 through the transmission of the reaction force F2 to the face.
The lower contact body 905 of the traction device 900 described above pushes the lower edge of the mandible in the posterior direction of the human body with the reaction force F2. This may inhibit the growth or movement of the mandible in the anterior direction.
The distance between the lower edge of the mandible and the forehead and the angle to the face formed by the lower edge of the mandible and the forehead vary relatively greatly with traction of the mouthpiece 901. At least one of the upper contact body 904 and the lower contact body 905 of the traction device 900 described above may lose the contact with appropriate positions on the face in a relatively short time. In such a case, the adjustment for pulling the maxilla in an appropriate direction may be complicated.
In this way, the traction device 900 described above may require a complicated procedure for appropriate encouragement of the growth or movement of the jaw.